PSL301H1 Chapter Notes - Chapter 3: Heart Valve, Heart Sounds, Diastole
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PSL301H1 Full Course Notes
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The heart contracts and relaxes during a cardiac cycle. Each cardiac cycle has two phase: diastole - relaxes, systole - contracts. Both relaxing atria willined with blood from veins, Av valves between them open and blood flow due to gravity. Some blood is squeezed back into the veins. Early ventricular contraction and the first heart sound. Atra contract: depolarization wave move through the conducting cells of a (cid:314) purkinje (cid:314) apex. Vibration following closure of the av valves creates the first heart sound, s1. Isovolumic ventricular contraction: high pressure but nowhere for blood to go (volume of blood in the ventricle is not changing ) An independent event: atrial muscle repolarizing and relaxing , and blood go from veins into atrium again. Ventricle contract, generate enough pressure to open semilunar valves. Closure of the semilunar valves create the second heart sound. Isovolumic ventricular relaxation because the blood volume in the ventricle is not changing.
